Lumbar packs combine some of the advantageous features of backpacks that have shoulder straps with fanny packs that have only a waistbelt. These lumbar packs are taller than fanny packs so that they may have the same volume or capacity as a small backpack with shoulder straps (day pack), but they carry the load on the person's hips rather than hanging the load on the person's shoulders. Consequently, lumbar packs have become popular for cyclist, climbers, and other athletic and recreational users by allowing the user to carry a significant load without restraining or burdening the chest and shoulders with the shoulder straps of a backpack.
As lumbar packs are made larger, however, the fit of the pack against the user's back is not optimal. The increased height of the lumbar pack results in a significant portion of the pack being located above and somewhat rearwardly from the waistbelt connection to the pack. In addition, as packs are made larger, the weight of the load carried therein increases similarly. This combination of a large load being vertically and rearwardly offset from the connection point of the pack to the supporting waistbelt results in a force couple with a downward vector extending through the center of gravity of the load and an upward vector extending through the connection point that tends to pivot the pack away from the user's back, which force couple is resisted only by the waistbelt. The load and pack are free to bounce and shift when in this position away from the user's back, causing fatigue and discomfort to the user. A conventional waistbelt attachment has insufficient rigidity and strength to provide much stability or resistance to such bouncing and shifting.
Consequently, the inventor of the present application developed an improvement for tall lumbar packs, disclosed in U.S. Pat. No. 5,025,965, wherein a diagonal strap is extended at an angle from an upper portion of the lumbar pack downwardly and forwardly to an attachment on the waistbelt that is spaced a distance forward from the connection of the waistbelt to the pack. The strap is adjustable so that the pack and load can be pulled snugly into a position against the user's back. The strap greatly improves the stabilization of lumbar packs against the back of the user.
The improvement realized by the diagonal strap is limited, however, by the position of the diagonal strap on the lumbar pack. The area of the pack located above the connection point to the diagonal strap remains unsupported. As a consequence, it is possible for the top of the pack which has no structural rigidity to fold and slump away from the user's back.
While frames have traditionally been used to provide support for all types of backpacks, they are not standardly used with lumbar packs. The added weight from a frame would be very undesirable in a lumbar pack, and frames are typically stiff and inflexible so that they do not conform to the contours of the user's back as the user bends and flexes during bicycle riding or hiking over rough terrain. Therefore, such traditional frames cause discomfort to the user.
Another disadvantage common to most lumbar packs in a lack of a means to retain the pack in an upright position to facilitate access to the inner compartment or compartments of the lumbar pack. Due to the pliant-sided nature of most lumbar packs, they tend to slump and droop when unsupported, such as when removed from the user. These characteristics are not conducive to access to the interior of the lumbar pack for inserting or removing objects into or from the lumbar pack.